An explosion hit a police building in southeastern Turkey's Diyarbakir province on Friday, according to Anadolu Agency.

The blast at Diyarbakir's Baglar police facility injured at least six people, according to security sources.

According to initial reports, the explosion took place at around 8 a.m. local time (0500 GMT) near a building used by riot police.

The blast also damaged nearby cars and premises.

An investigation is underway to discover the cause of the blast.

The explosion came after several Peoples' Democratic Party (HDP) lawmakers were detained early Friday for failing to appear for a summons to testify as part of a counter-terrorism investigation, Turkish security sources said.

Those detained include HDP co-chairs Figen Yuksekdag and Selahattin Demirtas, as well as the party's parliamentary group leader Idris Baluken.